1. Field of the Invention
This invention relates to a new and improved system for reducing materials to a smaller size. More particularly, it relates to a large-scale pre-grinding system for reducing rigid PVC pipe and other plastic materials for re-cycling.
2. Description of Related Art
Machines for reducing scrap material of the type including a pre-grinding system are known. A pre-grinding system may include a feed chute for receiving scrap material, a pre-grinder for processing the scrap material, a hydraulic cylinder unit for moving the scrap material from the feed chute into the pre-grinder, and other components suitable for handling and processing scrap material. For example, an exemplary pre-grinding system manufactured and sold by MILLER MANUFACTURING of Turlock, Calif. includes a MILLER PL 40 Pre-Grinder in combination with a MILLER PL2340 Feed Chute and a hydraulic cylinder unit. This pre-grinding system provides a high production, minimal maintenance mill capable of pre-grinding PVC pipe scrap for processing to a reusable powder form. This and other conventional systems are limited to processing PVC pipe with a maximum diameter of 36 inches. The present invention processes larger size pipe.
Conventional pre-grinding systems are limited in size due to the impracticability of merely increasing the dimensions of such systems. For example, increasing the size of the feed chute of conventional pre-grinding systems is undesirable because an operator would need to climb upon an external wall of the feed chute to view within a feed chamber of the feed chute. Merely increasing the size of a conventional pre-grinding system would also require the operator to climb upon the external wall to load materials into the feed chamber, increasing the likelihood that an operator will slip and fall into the feed chute. Furthermore, simply increasing the size of the feed chute would necessarily increase the size of feed chute covers. As such doors are typically made of xc2xdxe2x80x3 steel plate, increasing the dimensions of the doors would result in larger and heavier doors which would be unwieldy and inherently dangerous for the operator to control.
Conventional pre-grinders use rotor assemblies having a combination of single impact hammers and double impact hammers. For example, the rotor assembly of the prior art pre-grinders carried both single impact hammers having a single impact surface and double impact hammers having two fork-like impact surfaces. The combination of single and double impact hammers allows the single hammer to reduce any scrap material which the double hammer misses, particularly the area of scrap material which extends between the fork-like impact surfaces. A disadvantage of such prior-art machines is that two distinct types of hammers are necessary to design, manufacture, and inventory, which leads to increased costs of manufacturing, maintaining and repairing conventional pre-grinders.
Further, increasing the size of prior art pre-grinders by increasing the diameter of the rotor is unfeasible due to the difficulty in dynamically balancing the heavy mass of the rotor. Increasing the disc diameter of the rotors increases the dynamic loads upon the rotors, which disadvantageously increases wear-and-tear on prior art systems. In particular, the life span of a conventional rotor is limited because disc mounting holes for supporting the hammers wear, which hampers and/or prevents dynamic balancing of the rotor.
The pre-grinding system of the present invention overcomes the disadvantages of prior pre-grinder system systems discussed above. The pre-grinding system of the present invention reduces scrap materials such as PVC pipe and other rigid materials to chips, for example to chips measuring two inches or less. The pre-grinder system includes a pre-crusher for impact grinding the material, a feed chute for collecting the material, and a hydraulic cylinder section for transferring the material from the feed chute into the pre-crusher. One aspect of the present invention is directed to a feed chute trough having a feed chamber, an opening providing access into the feed chamber, and a recess downwardly extending from the opening, a feed chute cover pivotally connected to the feed chute trough and having an overhang corresponding to the recess which provides horizontal access into the feed chute for viewing the feed chamber.
Another aspect of the present invention is directed to a pre-grinding system including a feed chute trough, a feed chute cover pivotally connected to the feed chute trough, a hydraulic actuator for opening and closing the feed chute cover, and a counterbalance valve for dampening closure of the feed chute cover.
Another aspect of the present invention is directed to a pre-grinding system including a chamber, a cover for closing the chamber having an opened-loading position and a closed-operating position, and a gate providing access from the chamber into a pre-crusher, the gate having an opened-operating position and a closed-loading position, a hydraulic feed cylinder section for transferring the material from the feed chute into the pre-crusher, and a control system for controlling the cover, the gate, and the hydraulic cylinder section, in which the control system moves the gate from the closed-loading position to the opened-operating position only when the cover is in the closed-operating position.
Another aspect of the present invention is directed to a pre-crusher including a rotor assembly rotatably mounted to a housing of the pre-crusher, a first hammer pin transversely mounted on the rotor, a second hammer pin transversely mounted on the rotor, a plurality of identical hammer assemblies, each hammer assembly having a single impact portion. A single hammer assembly is rotatably mounted on the first hammer pin and a pair of hammer assemblies are rotatably mounted on the second hammer pin.
Yet another aspect of the present invention is directed to a pre-crusher including a rotor assembly having at least one disc, the disc having at least a pair of transversely extending primary holes for positioning a respective impact hammer pin, the pair of primary holes being diametrically opposed, the disc having at least a pair of transversely extending secondary wear holes, the pair of secondary wear holes diametrically opposed from one another and radially spaced between the primary holes.
It is an object of the present invention to provide a large feed chute which reduces or eliminates the need to cut pipe or scrap materials to a particular length before placing it into the pre-grinding system.
It is an object of the present invention to promote operator safety and increase machine life by dampening closure of a feed chamber cover.
It is a further object of the present invention to enhance safety of the operator by completely isolating the operator from the pre-crusher and the feed chamber by using a sequential control system which coordinates opening and closing of the feed chamber cover and a pre-crusher gate.
It is a further object of the present invention to provide a pre-grinding system with an interlocked hydraulically safety system in combination with a pre-crusher rotor assembly running at a substantially constant velocity during operation.
It is a further object of the present invention to efficiently and effectively reduce scrap material such as large diameter PVC pipe and other materials to chips with a single pass through the pre-crusher.
It is yet a further object of the present invention to increase the life span of a rotor assembly of the pre-crusher by providing secondary mounting holes for hammer pins of the rotor assembly.
The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention: